"South Korea's AA- rating balances robust external finances, steady macroeconomic performance, and sound fiscal management against evolving geopolitical risks related to North Korea and medium-term structural challenges from aging demographics and low productivity," the ratings agency said in a report posted on its website.

South Korea's economic growth momentum has slowed considerably over the past year as Asia's fourth largest economy weathers the effects of slowing global growth and US-China trade tensions, it added.

"Nevertheless, underlying growth performance remains sound and broadly in line with peers," Fitch Ratings said.

The rating agency said it forecasts South Korea's economic growth to slow to 2 percent in 2019 from 2.7 percent in 2018, noting the downturn in the semiconductor sector is driving a contraction in exports and weighing on facilities investment.

Semiconductors account for one-fifth of South Korea's outbound shipments. (Yonhap)